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<title>Section 13.7.&nbsp; ClientServer Model</title>
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<h3 class="docSection1Title" id="454331-803">13.7. ClientServer Model</h3>
<p class="docText"><a name="idd1e97862"></a><a name="idd1e97867"></a><a name="idd1e97872"></a><a name="idd1e97877"></a><a name="idd1e97882"></a><a name="idd1e97887"></a>A common use for a daemon process is as a server process. Indeed, in <a class="docLink" href="ch13lev1sec4.html#ch13fig02">Figure 13.2</a>, we can call the <tt>syslogd</tt> process a server that has messages sent to it by user processes (clients) using a UNIX domain datagram socket.</P>
<p class="docText">In general, a <span class="docEmphasis">server</span> is a process that waits for a <span class="docEmphasis">client</span> to contact it, requesting some type of service. In <a class="docLink" href="ch13lev1sec4.html#ch13fig02">Figure 13.2</a>, the service being provided by the <tt>syslogd</tt> server is the logging of an error message.</P>
<p class="docText">In <a class="docLink" href="ch13lev1sec4.html#ch13fig02">Figure 13.2</a>, the communication between the client and the server is one-way. The client sends its service request to the server; the server sends nothing back to the client. In the upcoming chapters, we'll see numerous examples of two-way communication between a client and a server. The client sends a request to the server, and the server sends a reply back to the client.</p>

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